U.S. patent number 10,968,533 [Application Number 15/053,870] was granted by the patent office on 2021-04-06 for feed system for crystal pulling systems.
This patent grant is currently assigned to Corner Star Limited. The grantee listed for this patent is SunEdison, Inc.. Invention is credited to Giorgio Agostini, Gianni Dell'Amico, Stephan Haringer, Renzo Odorizzi, Giancarlo Zago, Marco Zardoni.
United States Patent |
10,968,533 |
Haringer , et al. |
April 6, 2021 |
Feed system for crystal pulling systems
Abstract
A system for growing silicon crystal structures includes a
housing defining a growth chamber and a feed system connected to
the housing for delivering silicon particles to the growth chamber.
The feed system includes a container for holding the silicon
particles. The container includes an outlet for discharging the
silicon particles. The feed system also includes a channel
connected to the outlet such that silicon particles discharged from
the container flow through the channel. The feed system further
includes a separation valve connected to the channel and to the
housing. The separation valve is configured such that a portion of
the feed system rotates relative to the housing.
Inventors: |
Haringer; Stephan
(Castelbello/Ciardes, IT), Dell'Amico; Gianni
(Merano, IT), Zago; Giancarlo (Merano, IT),
Odorizzi; Renzo (Gargazone, IT), Agostini;
Giorgio (San Giacomo di Laives, IT), Zardoni;
Marco (Merano, IT) |
Applicant: |
Name |
City |
State |
Country |
Type |
SunEdison, Inc. |
Maryland Heights |
MO |
US |
|
|
Assignee: |
Corner Star Limited (Kowloon,
HK)
|
Family
ID: |
1000005468669 |
Appl.
No.: |
15/053,870 |
Filed: |
February 25, 2016 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20170247809 A1 |
Aug 31, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C30B
15/12 (20130101); C30B 15/14 (20130101); C30B
29/06 (20130101); C30B 15/04 (20130101); C30B
15/002 (20130101); C30B 15/20 (20130101); C30B
15/02 (20130101) |
Current International
Class: |
C30B
15/04 (20060101); C30B 15/00 (20060101); C30B
15/02 (20060101); C30B 15/12 (20060101); C30B
29/06 (20060101); C30B 15/14 (20060101); C30B
15/20 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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104947186 |
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Sep 2015 |
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CN |
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1338682 |
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Aug 2003 |
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EP |
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323286 |
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Jan 1991 |
|
JP |
|
WO 2014195980 |
|
Dec 2014 |
|
WO |
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WO-2014195980 |
|
Dec 2014 |
|
WO |
|
Other References
Invitation to Pay Additional Fees regarding PCT/US2017/019260 dated
May 31, 2017; pp. 1-12. cited by applicant.
|
Primary Examiner: Qi; Hua
Attorney, Agent or Firm: Armstrong Teasdale LLP
Claims
What is claimed is:
1. A system for growing silicon crystal structures comprising: a
housing including an upper dome and defining a growth chamber; a
feed system attached to the upper dome for delivering silicon
particles to the growth chamber, the feed system comprising: a
support mechanism for supporting the feed system; a container for
holding the silicon particles, the container including an outlet
for discharging the silicon particles, wherein the container is
maintained in a fixed positioned relative to the housing by the
support mechanism; a channel connected to the outlet such that a
flow of silicon particles discharged from the container flow
through the channel; barriers disposed in the channel to slow the
flow of the silicon particles through the channel, wherein the
barriers extend from a bottom of the channel in a direction
perpendicular to a direction of flow of the silicon particles
within the channel; a connection flange directly connect to the
housing; a separation valve directly connected to the connection
flange, the separation valve movable between an open position
allowing the silicon particles to flow through the separation valve
and a closed position preventing silicon particles from flowing
through the separation valve; and a rotation flange directly
connected to the separation valve and the channel, wherein the
channel rotates about the rotation flange, and wherein the channel
is disconnected from the outlet when the channel rotates about the
rotation flange to facilitate maintaining the system; and wherein
at least a portion of the upper dome is positioned between an
opened position and a closed position to facilitate cleaning the
system, and the channel moves with the upper dome as the upper dome
is positioned between the opened position and the closed position,
and wherein the container remains stationary in relation to the
housing as the upper dome and the channel are positioned between
the opened position and the closed position.
2. The system of claim 1, wherein the support mechanism comprises a
mount for fixedly mounting the feed system to the housing.
3. The system of claim 1, wherein the container remains
substantially stationary in relation to the housing as the channel
is rotated.
4. The system of claim 1, further comprising a feed system housing
including an access panel.
5. The system of claim 1 further comprising an actuator configured
to actuate the separation valve.
Description
FIELD
This disclosure generally relates to systems and methods for the
production of ingots of semiconductor or solar-grade material and
more particularly to systems and methods including feed systems for
delivering semiconductor or solar-grade feedstock material to a
crystal pulling system.
BACKGROUND
In the production of single silicon crystals grown by the
Czochralski (CZ) method, polycrystalline silicon is delivered into
and melted within a crucible, such as a quartz crucible, to form a
silicon melt. A puller lowers a seed crystal into the melt and
slowly raises the seed crystal out of the melt, solidifying the
melt onto the seed crystal. In the continuous Czochralski method, a
continuous flow of polycrystalline silicon is delivered into the
crucible to maintain the silicon melt at a substantially constant
level. The flow of polycrystalline silicon particles into the
crucible must be precisely controlled to control the purity and
quality of the formed single silicon crystals. A housing encloses
the crucible and defines a growth chamber.
At least some known systems for forming single silicon crystals
include a feed system attached to the housing for delivering the
polycrystalline silicon particles to the crucible. However, the
polycrystalline silicon particles may be contaminated by the feed
systems as the particles are delivered to the crucible. Moreover,
the feed systems may not deliver the polycrystalline silicon
particles to the crucible at a flow rate sufficient to match the
continuous extraction of melted silicon.
In some crystal growing systems, the feed systems must be detached
from the housing for maintenance and loading of the feed systems
and/or for maintenance of the crucible. However, detaching the feed
systems reduces the productivity of the systems. For example,
detaching or reattaching the feed systems may cause vibrations that
disturb the formation of the single silicon crystals. Therefore, at
least some crystal growing systems are shut down while the feed
systems are detached and reattached. Also, complicated engineering
and several hours of labor may be required to disassemble and
reassemble the feed systems due to the weight and size of the feed
systems.
Thus, there exists a need for a more efficient and effective system
to deliver a precise and continuous flow of polycrystalline silicon
particles to a crucible.
This Background section is intended to introduce the reader to
various aspects of art that may be related to various aspects of
the present disclosure, which are described and/or claimed below.
This discussion is believed to be helpful in providing the reader
with background information to facilitate a better understanding of
the various aspects of the present disclosure. Accordingly, it
should be understood that these statements are to be read in this
light, and not as admissions of prior art.
BRIEF SUMMARY
In one aspect, a system for growing silicon crystal structures is
provided. The system includes a housing defining a growth chamber,
and a feed system connected to the housing for delivering silicon
particles to the growth chamber. The feed system includes a
container for holding the silicon particles. The container includes
an outlet for discharging the silicon particles. The feed system
also includes a channel connected to the outlet such that silicon
particles discharged from the container flow through the channel.
The feed system further includes a separation valve connected to
the channel and to the housing. The separation valve is configured
such that a portion of the feed system rotates relative to the
housing.
In another aspect, a feed system for delivering silicon particles
to a crystal pulling system is provided. The system includes a
separation valve for connecting the feed system to a housing of the
crystal pulling system such that the silicon particles are
delivered to a growth chamber defined by the housing. The system
further includes a frame for maintaining the feed system in fixed
alignment with the growth chamber. The frame is connected to the
housing such that the housing can be opened to provide access to
the growth chamber.
In yet another aspect, a system for growing silicon crystal
structures is provided. The system includes a housing defining a
growth chamber, and a feed system connected to the housing and
configured for delivering silicon particles to the growth chamber.
The feed system includes a container for holding the silicon
particles. The container includes an outlet for discharging the
silicon particles, and an outlet extension configured such that a
layer of silicon particles collects adjacent the outlet extension.
The feed system further includes a channel for silicon particles
discharged from the container to flow through, and a liner. The
channel has an interior surface, and the liner is adjacent the
interior surface of the channel to inhibit the silicon particles
contacting the interior surface. At least one barrier is disposed
in the channel to slow the flow of silicon particles through the
channel.
Various refinements exist of the features noted in relation to the
above-mentioned aspects. Further features may also be incorporated
in the above-mentioned aspects as well. These refinements and
additional features may exist individually or in any combination.
For instance, various features discussed below in relation to any
of the illustrated embodiments may be incorporated into any of the
above-described aspects, alone or in any combination.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of a crystal pulling system.
FIG. 2 is a front view of the crystal pulling system shown in FIG.
1.
FIG. 3 is a front sectional view of a feed system for use in the
crystal pulling system shown in FIG. 1.
FIG. 4 is a side sectional view of the feed system shown in FIG.
3.
Corresponding reference characters indicate corresponding parts
throughout the several views of the drawings.
DETAILED DESCRIPTION
Referring to FIG. 1, a crystal pulling system is shown
schematically and is indicated generally at 100. FIG. 1 shows an
X-axis and a Y-axis for reference during the following description.
Unless otherwise noted, directions refer to the orientation of
crystal pulling system 100 shown in FIG. 1. Crystal pulling system
100 may be used to produce a single crystal ingot by a Czochralski
method. While the system is described in relation to the continuous
Czochralski method of producing single crystal ingots, a batch
process may be used.
The illustrated crystal pulling system 100 includes a housing 102
defining a growth chamber 104, a susceptor 105 supported by a
rotatable shaft 106, a crucible assembly 108 that contains a melt
110 of semiconductor or solar grade material (e.g., silicon) from
which an ingot 111 is being pulled by a crystal puller 113, and a
heating system 124 for supplying thermal energy to system 100. The
illustrated system 100 also includes a heat shield 123 configured
to shield ingot 111 from radiant heat from melt 110 to allow ingot
111 to solidify.
Housing 102 encloses susceptor 105, crucible assembly 108, and
portions of heating system 124. Housing 102 includes an upper dome
127, which may include one or more view ports to enable an operator
to monitor the growth process. In use, housing 102 may be used to
seal growth chamber 104 from the external environment. Suitable
materials from which housing 102 may be constructed include, but
are not limited to, stainless steel.
Crucible assembly 108 includes a crucible 130 having a base 131 and
a generally annular sidewall 133 extending around the circumference
of base 131. Together, base 131 and sidewall 133 define a cavity
135 of crucible 130 within which melt 110 is disposed. Crucible 130
may be constructed of any suitable material that enables system 100
to function as described herein including, for example, quartz.
Crucible assembly 108 also includes a plurality of weirs or fluid
barriers that separate melt 110 into different melt zones. In the
illustrated embodiment, crucible assembly 108 includes a first weir
137 (broadly, a fluid barrier) separating an outer melt zone 139 of
melt 110 from an inner melt zone 141 of melt 110, and a second weir
143 (broadly, a fluid barrier) at least partially defining a growth
zone 145 from which crystal ingot 111 is pulled. First weir 137 and
second weir 143 each have a generally annular shape, and have at
least one opening defined therein to permit melt 110 to flow
radially inward towards growth zone 145. First weir 137 and second
weir 143 are disposed within cavity 135 of crucible 130, and create
a circuitous path from outer melt zone 139 to inner melt zone 141
and growth zone 145. Weirs 137, 143 thereby facilitate melting
solid feedstock material 116 before it reaches an area immediately
adjacent to the growing crystal (e.g., growth zone 145). Weirs 137,
143 may be constructed from any suitable material that enables
system 100 to function as described herein, including, for example,
quartz. While the illustrated embodiment is shown and described as
including two weirs, system 100 may include any suitable number of
weirs that enables system 100 to function as described herein, such
as one weir, three weirs, or four or more weirs.
Crucible 130, first weir 137, and second weir 143 may be formed
separately from one another, and assembled to form crucible
assembly 108. In other suitable embodiments, crucible assembly 108
may have a unitary construction. That is, crucible 130 and one or
both weirs 137, 143 may be integrally formed (e.g., formed from a
unitary piece of quartz).
Crystal pulling system 100 further includes a feed system 112. As
will be described in more detail below, feed system 112 includes a
container 114 for holding feedstock material 116 and is configured
to provide feedstock material 116 to crucible 130. Feed system 112
is fixedly mounted to housing 102. Specifically, in the illustrated
embodiment, feed system 112 is connected to upper dome 127. At
least a portion of feed system 112, such as container 114, is
maintained in a substantially fixed position relative to housing
102. As a result, during setup and maintenance of crystal pulling
system 100, feed system 112 remains mounted on housing 102, which
simplifies operation of crystal pulling system 100. Moreover, feed
system 112 can be refilled during operation of crystal pulling
system 100 without disturbing the formation of single crystal ingot
111.
Feed system 112 is supported in fixed alignment with growth chamber
104 by support mechanisms including a mount 119, a plurality of
chains 121, and a collar 125. Mount 119, chains 121, and collar 125
are connected to a frame 129. Accordingly, mount 119, chains 121,
collar 125, and frame 129 maintain feed system 112 in a fixed
position during operation of crystal pulling system 100. In
alternative embodiments, feed system 112 is mounted to any portions
of crystal pulling system 100 in any manner that enables crystal
pulling system 100 to operate as described. In some embodiments, at
least a portion of feed system 112 is movable in relation to
crucible 130 to facilitate operation and maintenance of crystal
pulling system 100.
Feed system 112, and in particular container 114, may be sized to
hold at least the amount of feedstock material 116 required for a
complete growing cycle of single crystal ingot 111. As a result,
the risk of contamination and growth failure are reduced. For
example, operators are not required to provide additional feedstock
material 116, which may introduce contaminants, to feed system 112
during the growing cycle. Moreover, crystal pulling system 100
reduces the risk of operator exposure to hazardous materials.
During operation of crystal pulling system 100, feed system 112
supplies feedstock material 116 to crucible 130, which is melted to
form melt 110. Heating system 124 includes a plurality of heaters
126 positioned adjacent crucible 130 to provide heat for liquefying
or melting feedstock material 116 to form melt 110. A seed crystal
149 is lowered into and then slowly raised out of melt 110 to grow
single crystal ingot 111. As seed crystal 149 is slowly raised,
silicon atoms from melt 110 align with and attach to the silicon
atoms of ingot 111 allowing single crystal ingot 111 to grow larger
and larger. The raising of the silicon atoms from melt 110 causes
them to cool and solidify.
A controller 128 controls feed system 112 and heating system 124 to
maintain silicon melt 110 at a desired state for forming single
crystal ingot 111. Controller 128 is capable of supplying feedstock
material 116 while ingot 111 is raised from melt 110. For example,
controller 128 may control the addition of feedstock material 116
based at least in part on the mass of the silicon in crucible 130,
e.g., by measuring the weight or measuring liquid height of melt
110. In addition, the amount of current supplied to each of heater
126 by controller 128 may be separately and independently chosen to
optimize the thermal characteristics of melt 110. Controller 128
sends signals to and/or receives signals from any components of
system 100. For example, in the illustrated embodiment, controller
128 is coupled to and communicates with at least heating system
124, separation valve 122, and feed system 112.
As discussed above, during operation of system 100, puller 113
moves seed crystal 149 toward and away from melt 110 in a direction
perpendicular to the surface of melt 110 such that seed crystal 149
is lowered into melt 110 and then raised out of melt 110. As seed
crystal 149 is raised out of melt 110, single crystal ingot 111 is
formed. Characteristics of melt 110 such as temperature, pressure,
and purity are maintained at a predetermined level to produce a
high quality single crystal ingot 111. For example, the
introduction of foreign solid particles into melt 110 must be
minimized. Moreover, the purity of melt 110 is determined at least
in part by the purity of feedstock material 116 provided by feed
system 112.
In reference now to FIGS. 3 and 4, feed system 112 includes
container 114 defining an interior space 132 for holding feedstock
material 116. Container 114 may be constructed of any suitable
materials. In the illustrated embodiment, container 114 is made of
aluminum and is anodized to provide resistance to corrosion. In
alternative embodiments, container 114 is made of a material
similar to feedstock material 116 to inhibit contamination of
feedstock material 116. For example, in some embodiments, container
114 is made of quartz and/or silicon.
Container 114 includes a top wall 136, a bottom wall 138 opposite
top wall 136, and a sidewall 140 extending between top wall 136 and
bottom wall 138. Top wall 136 defines an inlet 142 for material to
enter interior space 132. Bottom wall 138 defines an outlet 144 for
material to exit interior space 132. Container 114 further defines
an interior surface 146. In particular, interior surface 146 is
defined by the portions of top wall 136, bottom wall 138, and
sidewall 140 facing interior space 132.
Top wall 136, bottom wall 138, and sidewall 140 of container 114
may have any suitable shape. In the illustrated embodiment,
sidewall 140 is substantially cylindrical and is closed at opposed
ends by top wall 136 and bottom wall 138. Top wall 136 is
substantially flat and circular. Bottom wall 138 is partially
angled and forms a conical shape. Accordingly, bottom wall 138
facilitates feedstock material 116 flowing through outlet 144.
Moreover, positioning outlet 144 in bottom wall 138 facilitates
feedstock material 116 flowing through container 114 due to
gravity. In alternative embodiments, container 114 has any walls
suitable for feed system 112 to operate as described.
A refill flange 134 is coupled to container 114 adjacent inlet 142
to facilitate providing feedstock material 116 to interior space
132 of container 114. Feedstock material 116 may be any material
suitable for forming melt 110. For example, in some embodiments,
feedstock material 116 includes polycrystalline silicon
particles.
Feed system 112 further includes a liner 148 adjacent interior
surface 146 to inhibit feedstock material 116 contacting interior
surface 146. In particular, liner 148 extends adjacent the
cylindrical portion of sidewall 140. In some embodiments, liner 148
may extend adjacent top wall 136 and bottom wall 138. Liner 148
inhibits container 114 from contacting and/or contaminating
feedstock material 116. As a result, container 114 can be made of
less expensive materials without increasing the risk of
contaminating feedstock material 116. Liner 148 may be any material
suitable to inhibit contamination of feedstock material 116. For
example, in some embodiments, liner 148 is made of quartz and/or
silicon. Additionally or alternatively, liner 148 includes a
plurality of tiles, such as silicon tiles, that cover portions of
container 114. In further embodiments, liner 148 is a coating
applied to interior surface 146. Liner 148 may have any thickness
that enables crystal pulling system 100 to operate as
described.
In the illustrated embodiment, an outlet extension 150 extends
adjacent outlet 144. Outlet extension 150 is configured to
facilitate feedstock material 116 forming a stagnant layer 154.
Stagnant layer 154 reduces the dust and powder flowing through
crystal pulling system 100. In some embodiments, at least some dust
and powder collects in stagnant layer 154. Moreover, stagnant layer
154 reduces the abrasion and wearing of bottom wall 138 and the
risk of contamination due to flowing feedstock material 116
contacting bottom wall 138. As such, bottom wall 138 can be made of
a less expensive material and feed system 112 requires less
maintenance.
In the illustrated embodiment, outlet extension 150 includes a
stand pipe 152 extending from outlet 144 such that feedstock
material 116 collects around stand pipe 152 and forms stagnant
layer 154 adjacent bottom wall 138. Stagnant layer 154 inhibits
flowing feedstock material 116 contacting bottom wall 138 as
feedstock material 116 is directed towards outlet 144. In
alternative embodiments, outlet extension 150 includes an inverted
cone that directs feedstock material 116 into outlet 144 and
facilitates feedstock material 116 collecting around outlet 144.
Outlet extension 150 may be any suitable material and have any
suitable thickness. In some embodiments, outlet extension 150 is
constructed of quartz.
Outlet extension 150 has a height 156 configured such that
feedstock material 116 collects around outlet extension 150 to form
stagnant layer 154 substantially covering bottom wall 138. For
example, in the illustrated embodiment, height 156 of stand pipe
152 is configured such that stagnant layer 154 has a surface angle
158 relative to the horizontal that is less than the angle of
repose of feedstock material 116. As used throughout this
description, the term "angle of repose" refers to the greatest
angle relative to the horizontal plane at which material lies
without slumping. In the illustrated embodiment, stagnant layer 154
forms a funnel shape to direct feedstock material 116 into outlet
144 through outlet extension 150.
Feedstock material 116 flows through outlet 144 and is provided to
a transport mechanism 118 where the material is directed through a
conduit 120. Transport mechanism 118 may be any mechanism
configured to transport feedstock material 116 through conduit 120.
Flow of feedstock material 116 through conduit 120 can be
controlled by transport mechanism 118. Suitably, the interior
surfaces of transport mechanism 118 and/or conduit 120 are covered
with a liner to inhibit material contacting the interior surfaces.
For example, in the illustrated embodiment, a plurality of tiles
160 are adjacent the interior surface of conduit 120. Tiles 160 may
be constructed of any materials that inhibit contamination of
silicon particles. For example, tiles 160 may be any of the
following, without limitation: quartz, silicon, and/or any other
materials suitable to inhibit contamination of silicon
particles.
In the example embodiment, transport mechanism 118 vibrates to
induce feedstock material 116 to flow through feed system 112. In
alternative embodiments, transport mechanism 118 has any
configuration that enables crystal pulling system 100 to operate as
described. In the illustrated embodiment, transport mechanism 118
is separated from container 114 and other portions of feed system
112 such that vibrations are not transmitted throughout the
entirety of feed system 112. As such, the generation of dust and
powder in feed system 112 is reduced. In addition, the wearing due
to vibrations of components of feed system 112, such as container
114, is reduced.
A housing 162 encloses transport mechanism 118 and conduit 120.
Housing 162 is airtight such that a vacuum force can be applied to
transport mechanism 118 and/or conduit 120 within housing 162.
Housing 162 includes access panels 164 that provide access to
transport mechanism 118 and/or conduit 120 for inspection and
maintenance. Suitably, access panels 164 include at least one of
the following, without limitation: a flange, a door, and/or a
removable panel. One access panel 164 is disposed on a side of
housing 162 and one access panel 164 is disposed on the bottom of
housing 162. In some embodiments, a vacuum source and/or a gas
supply can be removably connected to at least one of access panels
164. For example, access panel 164 on the bottom of housing 162
includes a flange for connecting to a vacuum source and/or a gas
supply. Accordingly, access panel 164 enables multiple purging
cycles to be performed after feed system 112 is refilled. In
alternative embodiments, housing 162 has any configuration that
enables feed system 112 to operate as described. In some
embodiments, access panels 164 include a viewport to enable
operators to view operation of feed system 112 without opening or
dismounting feed system 112.
A channel structure 166 includes a channel 168 and is coupled to
housing 162 such that material flows from conduit 120 into channel
168. The interior surface of channel 168 is covered by a plurality
of tiles 170 to inhibit feedstock material 116 contacting the
interior surface of channel structure 166 as feedstock material 116
flows through channel 168. In particular, substantially the entire
interior surface of channel 168 is covered by tiles 170. In
suitable embodiments, tiles 170 may be any suitable material. In
the illustrated embodiment, tiles 170 are constructed of a silicon
material to inhibit contamination from feedstock material 116
contacting and abrading tiles 170.
Tiles 170 may be connected to channel 168 in any suitable manner.
For example, in the illustrated embodiment, an adhesive connects
tiles 170 to channel 168. The adhesive is compatible with the
materials of tiles 170 and channel 168 and is configured to
withstand vibrations during operation of crystal pulling system
100. One example of a suitable adhesive is an epoxy amine
two-component adhesive. In alternative embodiments, mechanical
fasteners, welds, and any other suitable connection means may be
used to connect tiles 170 to channel 168. Tiles 170 may have any
suitable size. In some embodiments, tiles 170 have a thickness in a
range between about 1 millimeter (mm) and about 20 mm or between
about 2 mm and about 10 mm. In the example embodiment, tiles 170
have a thickness of approximately 5 mm.
Suitably, channel 168 is sloped to facilitate feedstock material
116 flowing through channel 168 in a direction away from container
114 and towards crucible 130. In the illustrated embodiment,
feedstock material 116 flows through channel 168 in a generally
downward direction. To control the flow rate of material through
channel 168, a plurality of barriers 172 are disposed in channel
168. Barriers 172 define a surface that extends into the flow path
of feedstock material 116. Accordingly, feedstock material 116
flowing through channel 168 strikes the surface of barriers 172 and
is disrupted and/or slowed. As a result, barriers 172 allow the
flow of feedstock material 116 to be controlled. For example,
barriers 172 reduce the flow rate of feedstock material 116 and,
thereby, reduce the deterioration of feed system 112 due to
feedstock material 116 flowing through channel 168.
Barriers 172 may have any suitable configuration. In the
illustrated embodiment, barriers 172 are substantially plate shaped
projections that extend from the bottom of channel 168 in a
direction perpendicular to the direction of flow. Accordingly, in
the illustrated embodiment, barriers 172 are substantially parallel
to each other. Any suitable number of barriers 172, including one,
may be disposed in channel 168. In the illustrated embodiment,
seven of barriers 172 are disposed in channel 168. In further
embodiments, barriers 172 may be omitted. The configuration of
barriers 172 may be determined based at least in part on the change
in elevation along channel 168. For example, the number and/or size
of barriers 172 may be increased as the change in elevation is
increased such that the flow rate remains at a desired level.
Barriers 172 facilitate the control of the flow of feedstock
material 116 to crucible 130. Barriers 172 allow the flow of
feedstock material 116 to be maintained at a speed which inhibits
surface disturbances of melt 110, e.g., splashes. In addition,
barriers 172 reduce the wearing of crucible 130 due to the flow of
feedstock material 116 into crucible 130. Moreover, barriers 172
reduce the generation of powder and dust in the crystal pulling
system 100.
Channel structure 166 is connected to housing 162 by connection
mechanism 174. Connection mechanism 174 includes any components
suitable to connect channel 168 to housing 162 such that channel
168 and conduit 120 are in flow communication. For example, in the
illustrated embodiment, connection mechanism 174 includes a bellows
176, a fixed flange 178, and a fast connecting flange 180.
Accordingly, connection mechanism 174 facilitates movement between
channel 168 and housing 162. Moreover, connection mechanism 174
enables quick connection and disconnection of channel 168 and
housing 162. Channel structure 166 further includes an access
flange 182, which facilitates maintenance and inspection of channel
168. In addition, access flange 182 provides for expansions of feed
system 112.
Feed system 112 further includes a separation valve 122 that
facilitates isolating feed system 112 from growth chamber 104 to
allow feed system 112 to be refilled with feedstock material 116.
Separation valve 122 is connected to channel structure 166 such
that separation valve 122 and channel 168 are in flow
communication. Separation valve 122 is also connected to upper dome
127 of housing 102 and in flow communication with growth chamber
104. Separation valve 122 is positionable between an open position
where feedstock material 116 is allowed to flow through separation
valve 122 and a closed position where feedstock material 116 is
inhibited from flowing through separation valve 122. In some
embodiments, separation valve 122 is positionable in a plurality of
intermediate positions to facilitate control of the rate of flow
through separation valve 122. Separation valve 122 may be any valve
suitable to control the flow of feedstock material 116. For
example, in some embodiments, separation valve 122 may be any of
the following valves, without limitation: a gate valve system and a
ball valve system. Suitably, separation valve 122 is actuated by an
actuator 183, which may be automatic. In some embodiments, feed
system 112 is configured to inhibit feedstock material 116 falling
directly onto separation valve 122 to reduce the risk of separation
valve 122 malfunctioning and/or leaking. In further embodiments,
separation valve 122 is configured to resist malfunctioning and/or
leaking due to particles in separation valve 122.
A rotation flange 184 connects separation valve 122 and channel
structure 166 and is configured to enable rotation of feed system
112 relative to housing 102. In particular, channel structure 166
of feed system 112 rotates about rotation flange 184. Channel
structure 166 may be disconnected from other portions of feed
system 112 such as housing 162 and rotated to allow access to
system 100 without dismounting feed system 112 from system 100.
Rotating feed system 112 may allow access to housing 102 for
cleaning crystal pulling system 100 without dismounting feed system
112. In addition, crystal pulling system 100 may be recharged
during a running batch without dismounting feed system 112. In some
embodiments, portions of feed system 112 such as container 114 and
transport mechanism 118 remain stationary as portions of feed
system 112 are moved. Feed system 112 may rotate any amount
relative to puller 113. Suitably, feed system 112 can rotate at
least 90.degree. relative to puller 113.
During cleaning and maintenance of crystal pulling system 100,
housing 102 of crystal pulling system 100 may be opened to clean
crucible 130 or other components of crystal pulling system 100.
Rotating a portion of feed system 112 facilitates housing 102 being
opened. For example, in the illustrated embodiment, at least a
portion of upper dome 127 is opened to facilitate cleaning crystal
pulling system 100. Channel structure 166 is connected to upper
dome 127 and moves with upper dome 127 as upper dome 127 is
positioned between opened and closed positions. Channel structure
166 may be rotated and disconnected from portions of feed system
112 to enable upper dome 127 to be opened and closed. As a result,
portions of feed system 112 may remain aligned in relation to
growth chamber 104 when housing 102 is opened for cleaning and
maintenance.
A doping mechanism 188 is connected to feed system 112 and allows
for precise handling of a dopant that is provided to crucible 130.
Any suitable doping mechanism 188 may be used. For example, PCT
Patent Publication No. WO 2014/195980, which is incorporated by
reference in its entirety, describes a suitable doping mechanism.
By synchronizing doping mechanism 188 and feed system 112, a
desired flow of dopant and silicon particles can be provided to
melt 110 within crucible assembly 108. Accordingly, manual
intervention during operation of system 100 can be minimized. As a
result, risk of contamination and harm to operators can be
reduced.
Channel structure 166 has separate branches that form a Y-shape.
The separate branches are connected to conduit 120, doping
mechanism 188, and puller 113. Feedstock material 116, which in
some embodiments includes the dopant and silicon particles, is
provided to crucible 130 via the lower branch and separation valve
122. A connection flange 186 is connected to separation valve 122
to enable connection of separation valve 122 to housing 102.
Silicon particles and the dopant are introduced into channel 168
through separate upper branches and combined within channel 168.
Doping mechanism 188 is positioned in relation to separation valve
122 such that dopant is introduced to feed system 112 upstream of
separation valve 122 and flows substantially downward toward
separation valve 122. For example, in the illustrated embodiment,
doping mechanism 188 is above and approximately vertically aligned
with separation valve 122 such that the dopant flows directly
downward. As a result, crystal pulling system 100 has a
configuration that allows doping mechanism 188 to provide a
relatively large quantity of dopant throughout operation of crystal
pulling system 100. After traveling through channel 168, feedstock
material 116 is provided to crucible 130.
In some embodiments, a crystal pulling system includes a feed
system mounted to a housing. The feed system is configured to be
movable in relation to the housing such that maintenance of the
crystal pulling system can be performed without dismounting the
feed system. The feed system is configured to reduce dust and
powder flowing through the crystal pulling system. For example,
some embodiments include an outlet extension configured such that a
layer of feed material collects adjacent the outlet extension. In
addition, the feed system provides improved control of the flow of
material delivered to the crucible. Moreover, the crystal pulling
system is configured to require less maintenance than known systems
and provide increased automation of the growing process.
The crystal pulling systems and methods described above achieve
superior results compared to some known systems and methods. The
crystal pulling systems reduce the risk of material contamination.
As a result, the impurity accumulation in the silicon melt deriving
from contamination in the systems is reduced. The systems also
provide improved control of material flow through the systems.
Moreover, the systems have reduced abrasion and wearing.
Accordingly, the lifecycle of the system is increased and
generation of powder and dust during operation is reduced. The
system has improved operating efficiency which increases overall
production and reduces operating costs. Moreover, the safety risks
to operators during operation and maintenance of the systems is
reduced.
When introducing elements of the present invention or the
embodiment(s) thereof, the articles "a", "an", "the" and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising", "including" and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements. The use of terms indicating a particular
orientation (e.g., "top", "bottom", "side", etc.) is for
convenience of description and does not require any particular
orientation of the item described.
As various changes could be made in the above constructions and
methods without departing from the scope of the invention, it is
intended that all matter contained in the above description and
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
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